Also known as helicopter parents—or that couple from the PTA meeting that gasped when you admitted to buying Lunchables for your kid—these moms and dads monitor everything their children eat, watch and read.

Their parenting habits are as illiberal as their politics are liberal. After all, it wasn't conservatives who shot down Portland's fluoridation efforts for the fourth time, even though water fluoridation helps prevent tooth decay.

And these are, by and large, the same parents who might think that Mayor Michael Bloomberg's effort to limit poor people's ability to buy sugary drinks with food stamps is onerous and paternalistic — even if they would never let their own children touch something that wasn't organic.

While, in Oppenheimer's telling, in the past, "only right-wingers would sacrifice children's health to their own psycho-political neuroses," now liberals are letting fear govern their parenting techniques. And whereas the right-wing parents fear the government, these left-wing parents fear a lack of purity:

On the right, these mental illnesses stem from fear of government. On the left, their origins are a bit harder to pin down, but as I see it, they stem from an old mix of righteousness and the fear of contamination—from what we might recognize as Puritanism.

Generally, one might expect liberals who become parents to remain open-minded and flexible. After all, the very notion of liberality is bound up with freedom, while conservatism is ostensibly concerned with keeping things from breaking apart. But as Oppenheimer notes, it's today's liberal parent who has come to fear freedom:

One mother was trying to keep her daughter from eating a cupcake, because of all the sugar in cupcakes. Another was trying to limit her son to one juice box, because of all the sugar in juice. A father was panicking because there was no place, in this outdoor barn-like space at some nature center or farm or wildlife preserve, where his daughter could wash her hands before eating [...]Like any moral panic, nobody was immune to its contagion. Soon, I was fretting—but for different reasons. For all I knew, some of these kids weren't immunized, and they were fed only unpasteurized milk. The other parents were worried about germs and microbes and genetically modified apricots—I was worried about the parents. I was surrounded by the new Puritans: self-righteous, aspiring toward a utopian perfectionism, therefore condemned to perpetual anxiety—and in their anxiety, a threat to me and my children.

At the same time, conservative parents have generally become relatively more open-minded. Lenore Skenazy was famously called the worst mom in America after admitting that she let her 9-year-old ride New York's subway home alone. But really, she's just instilling her kids with self reliance and pull-yourself-up- by-your-bootstraps-grit. Skenazy's Free Range Kids movement supports events like "Take Our Children to the Park and Leave Them There Day," which is both self-explanatory and (potentially) horrifying. And yet none of her children has gone missing or been taken away by the authorities.

All those liberal worries about about obesity, high blood pressure, germs, autism and industrial chemicals, is leading to a lot of stress, which may in the end be more harmful than anything. Your bickering about the virtues of antibacterial hand lotion might give your kid a complex. Oppenheimer writes:

We know from research—which I have read—that stress increases the risk of various ailments, including cardiovascular disease. And sociologists have shown that children thrive best when they live with two parents in a low-conflict marriage. So it follows that if concerns about our children's health cause the children stress, or if they become a source of conflict between the parents, they may actually be counterproductive.

And while Oppenheimer's solution is simplistic—basically, calm down—it might be a good place to start. "Between the heyday of Progressive reform and our current Puritan moment, there was another possibility on the left: the hippie ethos of not worrying so much," Oppenheimer writes. So maybe just chill out, okay?